The invention relates to an individual rotor blade control device.
Conventional control devices for helicopter main rotors include a swash plate for transmitting the pilot""s control movements from the non-rotating system of the helicopter cabin to the main rotor system, which turns during operation. The swash plate can tilt to all sides for sinusoidal, monocyclic rotor blade adjustment and is axially displaceable for collective rotor blade adjustment. The swash plate, which serves as the primary control means, is actuated by several control elements or control rods arranged beneath the swash plate.
Low vibration levels, better flight performance and lower noise level emission can be achieved by superimposing additional blade angle modifications on the collective and sinusoidal, monocyclic blade angle adjustment, e.g. in order to counteract rotor blade induced oscillation. For this purpose, actuators that are individually allocated to the rotor blades are provided, with the actuators"" control movement being superimposed on the control movement of the swash plate. For safety reasons each actuator contains a safety device in order to bring it into a specified position and keep it there, as required. The actuators can be arranged, for example, between the rotating part of the swash plate and the connections of the individual rotor bladesxe2x80x94the linkages. If they are blocked by safety devices, they act like simple control rods so that the control movements of the swash plate can be transmitted reliably even when the actuators are switched off.
In Blaas, icebreaker, xe2x80x9cAufbau und Untersuchung einer aktiven Rotorblattsteuerungxe2x80x9d [Design and Examination of an Active Rotor Blade Control, BMFT Final Report, December 1990], apparent is a hydraulic actuator equipped with a spring acting in the adjusting direction, serving the purpose of bringing the actuator, as necessary, into a final position and holding it there. This actuator is characterized by a simple design. The disadvantage of the system securing it in a final position is that all actuators assume their final positions when the safety device is triggered and thus all rotor blades are subject to the same change in the blade angle. This so-called universal jump affects a sudden change in the thrust generated by the helicopter main rotor, which is problematic in particular when flying close to the ground.
For this reason actuators were developed that contain a safety device, which keeps the actuator in a centered position when the safety device has been triggered. The design of these actuators is more complex, and they weigh more.
The invention is based on the task of equipping the individual rotor blade control device with actuators of a simple design, where the negative effects of a universal jump are avoided.
This task is resolved by the rotor blade control device. Although, due to the opposed setting of the blade angle rate, which result from the actuators being in their final positions, different lifting values are generated on the individual rotor blades, and an accordingly deviating track. Relative to the entire rotor, the flight mechanical effects of the individual blade angle changes are mutually compensating.
In an advantageous design of the invention, the setting angle changes of adjacent rotor blades are of an opposed direction as a result of securing the actuators in their final positions so that alternating setting angle changes occur from blade to blade. In the case of more than six rotor blades, different distributions of the rotor blades also fulfill the criterion of mutually compensating for flight mechanical effects, i.e. avoiding peripheral pitching moments. The only thing that must be ensured is that half the rotor blades be adjusted in the opposed directions due to the securing of the actuators and that, additionally, all rotor blades that are set in one direction are distributed among sub-groups that are evenly distributed at the periphery. In the simplest case, i.e. from blade to blade alternating angle of reflection, these sub-groups consist of only one rotor blade each.
In another design of the invention, each actuator is designed as a linear actuator with two sub-assemblies which can move in relation to each other, wherein each sub-assembly has a coupling point and that the coupling points have a minimum distance in a first final position and a maximum distance in a second final position. Nevertheless, the invention can basically also be implemented with other actuator designs, such as, for example, rotating actuators.
In a further development of the invention, two actuator designs are used, wherein adjacent to a rotor blade with one actuator, which can be fastened in the first final position, a rotor blade with an actuator, which can be fastened in the second final position, is arranged. In this design, the connections of the actuators on the swash plate or on the individual rotor blades can have the same design for each rotor blade. It is also possible, however, to use actuators with the same design, which can all be fastened in the same final position and affect the opposed setting angle change by equipping half of the actuators with a turning element.
In one design of the invention, the safety device includes a pre-stressed element that can be expanded parallel to the adjusting direction of the actuator, e.g. a spring, which is arranged between the two sub-assemblies, which are movable in relation to each other, of the actuator and which serves the purpose of bringing the sub-assemblies into a final position and holding them there. Instead of a spring, a pre-stressed gas operated storage can also be used.